The present application generally relates to innovations and improvements in vehicle suspensions. More particularly, the present application relates to a linkage system that may be used in a vehicle suspension, and may be useful in multiple axle (i.e., tandem or tridem) on-off highway truck applications, or be applied to a single axle, such as a 4×2 commercial vehicle.
A typical trailing arm or trailing beam style air suspension achieves its primary roll stiffness property from the springing medium that reacts the vertical load and provides a vertical spring rate that will resist body roll. The spring rate developed by the air springs used in the suspension is low, however, when compared to a suspension using a mechanical spring. Consequently, additional roll stiffness has typically been required to be added to the air suspension to provide the desired overall roll stability characteristics.
As an example, on North American trailing arm suspensions, the rigid attachment of the arm to the axle together with the axle's torsional stiffness develops auxiliary roll stiffness. Essentially, a single wheel input on one side of the axle will move the axle along an arced path, the radius of the arc being a function of the length and pivot point of the trailing arm or beam. This motion will cause a relative angular change between one axle end and the other—resulting in a torsional load path through the axle. The section properties of the axle and its resultant resistance to torsional input will influence the auxiliary roll stiffness developed. The vertical stiffness of the front limb of the trailing arm (that portion of the arm that is forward of the axle) will also greatly impact the overall roll stiffness of the suspension.
As another example, on typical linkage air suspensions in Europe an “anti-roll bar” or “sway bar” has been utilized as the mechanism to achieve auxiliary roll stiffness. In the Hendrickson HTB suspension design embodied in U.S. Pat. No. 6,527,286, the auxiliary roll stiffness is achieved by the use of a torsionally stiff torque box (40) that is attached between the frame (via a cross member assembly) and the axle. The axle and control rods are attached by rubber bushed pivot connections and the axle undergoes minimal torsion or “twist” during axle cross articulation or opposed vertical travel side to side.
It would be desirable to provide a vehicle suspension wherein auxiliary roll stiffness is achieved without the addition of a roll-resisting device such as a torque box, or without the addition of an “anti-roll bar” or “sway bar.” Moreover, typical suspensions that twist the axle are highly torque reactive. Therefore it would be desirable to provide a vehicle suspension that is non-torque reactive, meaning that it is generally free of significant axle wind-up or torque.